Polyacetylene soluble

Even with improvement in properties of polyacetylenes prepared from acetylene, the materials remained intractable. To avoid this problem, soluble precursor polymer methods for the production of polyacetylene have been developed. The most highly studied system utilizing this method, the Durham technique, is shown in equation 2. 

Copolymerizations of benzvalene with norhornene have been used to prepare block copolymers that are more stable and more soluble than the polybenzvalene (32). Upon conversion to (CH), some phase separation of nonconverted polynorhornene occurs. Other copolymerizations of acetylene with a variety of monomers and carrier polymers have been employed in the preparation of soluble polyacetylenes. Direct copolymeriza tion of acetylene with other monomers (33—39), and various techniques for grafting polyacetylene side chains onto solubilized carrier polymers (40—43), have been studied. In most cases, the resulting copolymers exhibit poorer electrical properties as solubiUty increases. 

Oxidative polymerization of trans-bis-deprotected 79 under Hay coupling conditions [54] yielded, after end-capping with phenylacetylene, the high-melting and readily soluble oligomers 80a-e with the poly (triacetylene) backbone [87,106] (Scheme 8). Poly(triacetylene)s [PTAs,-(C=C-CR=CR-C=C) -] are the third class of linearly conjugated polymers with a non-aromatic allcarbon backbone in the progression which starts with polyacetylene [PA,... 

The soluble nonconjugated precursor polymer route to Durham polyacetylene via thermal elimination. 

Shirakawa polyacetylene, 444 Siloxanes, polymerization, 239 Size exclusion chromatography, 262-263 Solubility, specialty polymers, 256 Spacers, flexible polymer backbones, 97 Specialty polymers, polar/ionic groups, 256 Stability, polymers, 256 Storage moduli, vs. temperature behavior, 270... 

A route to processible polyacetylene, devised initially using classical initiators (Scheme 1i) 576-578 has been developed using well-defined molybdenum initiators to prepare conjugated polymers.579-585 They have also been employed to prepare polyacetylene via the polymerization of cyclooctate-traene, COT,586 and by the isomerization of poly(benzvalene).587 588 Substituted, and hence soluble, polyacetylene derivatives may be synthesized by polymerizing monosubstituted COT substrates.589-591... 

Durham route, the metathesis polymerization of 7,8-bis(trifluoromethyl)tricyclo[4.2.2.0]deca-3,7,9-triene gives a high-molecular weight soluble precursor polymer that is thermally converted to polyacetylene (equation 19.6). The precursor polymer is soluble in common organic liquids and easily purified by reprecipitation. The end product can be aligned giving a more compact material with bulk densities on the order of 1.05 —1.1 g/cm. ... 

Langsdorf BL, Zhou X, Adler DH, Lonergan MC. Synthesis and characterization of soluble, ionically functionalized polyacetylenes. Macromolecules 1999 32 2796-2798. 

A water-soluble salt of the above synthetic helical polyacetylene derivative, (I), in the current application having no asymmetric carbon atom was prepared by Sakajiri et al. (1) and used in biological research associated with biomimesis. 

A new class of mesogen consisting of polyacetylene derivatives, (II), containing aliphatic spacers was prepared by et al. Tang (3), which had high solvent solubility, moderate melting points, and excellent tractability. 

The three most widely used species of Echinacea are Echinacea purpurea, E pallida, and E angustifolia. The chemical constituents include flavonoids, lipophilic constituents (eg, alkamides, polyacetylenes), water-soluble polysaccharides, and water-soluble caffeoyl conjugates (eg, echinacoside, chicoric acid, caffeic acid). Within any marketed echinacea formulation, the relative amounts of these components are dependent upon the species used, the method of manufacture, and the plant parts used. Epurpurea has been the most widely studied in clinical trials. Although the active constituents of echinacea are not completely known, chicoric acid from E purpurea and echinacoside from E pallida and E angustifolia, as well as alkamides and polysaccharides, are most often noted as having immune-modulating properties. Most commercial formulations, however, are not standardized for any particular constituent. 

Unlike polyacetylene, substituted polyacetylenes are amorphous, electrically insulator soluble polymers.413 They are highly stable and not sensitive to oxidation. Since the substituents exert a strong steric effect, the polyene backbone is not copla-nar, and as a result, only limited conjugation is possible. 

The aromatic residue may be any of a large number of such units but the favourite for academic study has been the perfluoromethylxylene derivative shown, which smoothly eliminates at around room temperature to give a polyacetylene containing 25 % of trans- and 75 % of m-units. After transformation and isomerization at 80 °C, the polyacetylene produced is a continuous dense film. The physical chemistry of the transformation and isomerization reactions has been studied in detail229,230) and the properties of the polyacetylene are reviewed 231). The great advantage of this route is that the precursor is a soluble polymer so that it can be characterized and the physical form of the polyacetylene can be controlled. 

In 1982, Soga et al. 256> showed that exposure of acetylene to AsFs at low temperatures leads to rapid polymerization (in our experience this reaction can be explosively violent). The product is a solid polymer which is heavily arsenic-doped and has a conductivity several orders of magnitude lower than a conventional sample of polyacetylene saturation-doped from the gas phase. Aldissi and Liepins 2S7) have adapted this reaction to the preparation of soluble polyacetylene by adopting AsF3 as the reaction solvent. They claim that polymerization of acetylene with AsF5 is very rapid, giving a polymer which is soluble in common solvents. However, elemental analysis shows that the polyacetylene formed contains about one As atom per 10 CH units and this is not removed on repeated reprecipitations. It seems likely that the As atoms form part of the chain backbone, conferring sufficient flexibility to allow dissolution. It is claimed that films of soluble polyacetylene can be doped but very little information has been published. 

Polyacetylene may also be produced from a soluble precursor polymer by the Durham route, described earlier. In- this case the soluble precursor can be studied by conventional solution methods, provided that it is kept cold enough to prevent transformation. The molecular weight of the precursor has been determined by light scattering and low-temperature GPC 326) and corresponds to a polyacetylene chain with a molecular weight of about 200,000, with Mw/Mn of about 2. 

---